The present application corresponds to Japanese Patent Application No. H10-374548, filed Dec. 28, 1998, in Japan, the entire contents of which are hereby incorporated herein by reference.
1. Field of the Invention
The present invention relates to a substrate processing devices that subjects a substrate to a prescribed process.
2. Description of Related Art
The surfaces of substrates are subjected to many prescribed processes in the production of electronic devices such as LSIs (large-scale integrated circuits) and display devices such as liquid crystal displays. For example, the production of an LSI involves film deposition processes to form various conducting films and insulating films on the surface of a substrate, and etching processes to form prescribed patterns in the substrate surface. The substrate processing apparatus that performs this sort of substrate processing can be broadly divided into batch processing apparatus that process a plurality of substrates all at the same time, and single substrate-processing apparatus that process substrates individually. A common type of batch processing apparatus is an oxidization apparatus that uses a furnace, but a single-substrate-processing apparatus is often used for film deposition and etching to achieve better uniformity and reproducibility of the processing on different wafers.
The simplest configuration of a single-wafer processing apparatus is a process chamber that performs a prescribed process. In this configuration, substrates are individually transferred into and processed in the process chamber, and are individually removed therefrom. However, a problem with such a configuration is that the interior of the process chamber is exposed to the outside atmosphere whenever a substrate is inserted or removed, thus impairing the processing quality. In particular, when the process chamber is a vacuum chamber that uses a vacuum, such as in a film deposition apparatus or an etching apparatus, opening the chamber to the atmosphere when inserting and removing a substrate makes it necessary to evacuate the process chamber every time a process is performed, leading to poor productivity. To avoid such problems, a load lock chamber is normally provided in which the substrate is left temporarily when it is inserted and removed, and this load lock chamber is hermetically connected to the process chamber. When the gate valve between the process chamber and load lock chamber is open, the gate valve on the atmospheric side of the load lock chamber is kept closed, so the process chamber is not directly exposed to the atmosphere in this configuration.
On the other hand, with the increasing functionality and complexity of manufactured products such as electronic devices, the processes to which substrates are subjected have also become more complex. Specifically, these products tend to be produced by performing many different processes on a substrate. In the abovementioned apparatus that uses a vacuum environment, it would be desirable to have the ability to perform different processes consecutively in vacuo. This is because if the next process is performed once the substrate has been re-exposed to the atmosphere, the atmospheric exposure can result in contamination of the substrate surface.
To meet this demand for consecutive in vacuo processing, multi-chamber type apparatus equipped with a plurality of process chambers have been developed. The first multi-chamber type apparatus to be developed was an in-line apparatus where a plurality of process chambers were arranged in a row. A transfer mechanism was used to transfer substrates in vacuo along the arrangement of the plurality of process chambers, thereby performing consecutive processing by transporting the substrates to each process chamber in turn. Separation chambersxe2x80x94which are fitted with a robot to transfer substratesxe2x80x94are often disposed between each process chamber to prevent cross-contamination of the atmospheres between each process chamber. In other words, the plurality of process chambers are arranged with separation chambers interspersed between them.
However, in the abovementioned in-line apparatus, the line gets longer every time the number of process chambers is increased to allow a greater number of processes to be performed. The number of intervening separation chambers also increases as the number of process chambers increases, and so there has been the disadvantage that the line gets progressively longer. As a result, there have been disadvantages in that the apparatus takes up a greater area and the configuration of the transfer mechanism gets more complex.
Cluster tool type apparatus has been developed to solve such drawbacks. A cluster tool type apparatus has a configuration whereby a plurality of load lock chambers and a plurality of process chambers are arranged around a single separation chamber. Cluster tool type substrate processing apparatus are currently in widespread use in single-substrate processing applications. FIG. 7 is an outline plan view of a cluster tool type substrate processing apparatus as one example of a conventional substrate processing apparatus.
The apparatus shown in FIG. 7 consists of a centrally provided separation chamber 8, with a plurality of process chambers 1 and load lock chambers 2 disposed around separation chamber 8. Each of the chambers 1, 2 and 8 is equipped with a dedicated or shared evacuation system, and is thereby pumped down to the prescribed pressure. Also, a gate valve 5 is provided at the connection positions of each chamber 1, 2 and 8. A transfer mechanism 42 is provided inside separation chamber 8 as a transfer mechanism to transfer substrate 9 in vacuo.
A processed substrate 9 is accommodated in load lock chamber 2 by an auto loader (not illustrated). A substrate 9 inside load lock chamber 2 is sequentially transferred into process chamber 1 by transfer mechanism 42 provided inside separation chamber 8, and is subjected to the prescribed processing. When the prescribed series of processes on substrate 9 has been completed, substrate 9 is put back in load lock chamber 2 by transfer mechanism 42. After that, it is taken out to the atmosphere by the auto loader (not illustrated).
In the abovementioned cluster tool type substrate processing apparatus, the plurality of process chambers is not disposed in a linear fashion, but is disposed in a ring around a single separation chamber. Consequently, it has advantages in that it is possible to reduce the area it takes up compared with an in-line type of apparatus, and in that the configuration of the transfer mechanism is not complex.
However, recent further increases in the complexity and speed of substrate processing and the increasing size of substrates have meant that even the cluster tool type apparatus described above is starting to reach the limits of its capabilities. Specifically, now that the processes performed on substrates are becoming even faster and more complex due to the demand for devices with greater integration density, increased functionality and lower cost, it is becoming necessary to equip the apparatus with even more process chambers. There are two main reasons why the number of process chambers must be further increased. One is that the number of processes to be performed on substrates is continuing to increase, as mentioned above. The other is to divide the same process between a plurality of chambers in order to increase throughput.
If one tries to increase the number of process chambers in the layout shown in FIG. 7, the perimeter of the separation chamber has to be increased. That is, the cross-sectional area of the separation chamber has to be increased. As the separation chamber gets larger, the apparatus takes up a correspondingly larger area. Also, as the chamber increases in size, the vacuum pump system that evacuates it must also be made more large scale. But the separation chamber itself is essentially wasted space as far as the substrate processing is concerned, so that the cost of the apparatus is needlessly increased by increasing the area taken up by this space and by increasing the scale of the vacuum pump system.
Also, as the cross-sectional area of the separation chamber increases, it becomes necessary to increase the size of the transfer robot""s hand in the transfer mechanism, and its stroke length and transfer distance also increase. As a result, there is a problem in that the transfer mechanism also becomes more large-scale.
Furthermore, an apparatus of this sort is normally used by disposing it in a clean room whose interior cleanliness is kept at a prescribed level. As the area taken up by the apparatus increases, the clean room must be made correspondingly larger. A larger clean room requires more effort to keep the interior cleanliness at a prescribed level, leading to increased costs. It is therefore advantageous to make the constituent chambers of the apparatus as small as possible.
Another way of increasing the number of processes and increasing throughput is to increase the number of substrate processing apparatus. Specifically, this could be achieved by providing two sets of the apparatus shown in FIG. 7, with similar or different processes performed in each process chamber. However, this approach suffers from the problem that a substrate is exposed to the atmosphere when it is transferred from one apparatus to the next. And, although it is necessary only to increase the number of process chambers, this approach also increases the number of transfer mechanisms, load lock chambers and the like, and thus involves a considerable amount of unnecessary investment. There is also a problem in that two sets of apparatus take up twice as much area, thereby increasing the costs associated with maintaining the abovementioned degree of cleanliness.
One method of solving the aforementioned problems has been disclosed in JP10-55972, which claims the priority of U.S. patent application No. 08/644,636 now U.S. Pat. No. 6,176,667. In this disclosed system, a large load lock chamber 15 is disclosed which is connected to a transfer chamber 30 by doors 18, 19. A plurality of processing chambers A1, A2 are also connected to the transfer chamber 30 by doors 22. To save space, the processing chambers A1, A2 are arranged in a stacked, vertical configuration. One drawback of this disclosed system is that the load lock chamber 15 is designed large enough to accommodate a wafer cassette 12 that supports up to 100 wafers. Accordingly, each time the load lock chamber 15 is opened to the atmosphere to replace the wafer cassette 12, it takes a long time to again reduce the pressure in the load lock chamber 15 to a level that is sufficiently close to the processing pressures in the processing chambers A1, A2. Alternatively, a large-scale pump must be used.
As an alternate embodiment, JP10-55972 discloses the use of a group of smaller load lock chambers 61, 62, 63 in FIG. 4. Even the smaller load lock chambers 61, 62, 63 are designed to hold at least two wafers.
In both embodiments of JP10-55972, it is possible to have contamination (such as dust particle contamination) between the plurality of wafers loaded in one of the load lock chambers 15, 61, 62, 63. It is also possible to have contamination between one or more of the load lock chambers 15, 61, 62, 63 and the transfer chamber 30.
The invention of the present application has been made in order to solve problems such as those described in the preceding section, and aims to provide a practical substrate processing apparatus that does not take up a greater area as the number of chambers is increased.
To solve the abovementioned problems according to the present invention, a substrate processing apparatus comprises a centrally provided evacuable separation chamber, a plurality of individually evacuable load lock chambers and a plurality of evacuable process chambers which are hermetically connected to the sides of the separation chamber via gate valves, and a transfer mechanism provided inside the separation chamber. The transfer mechanism removes a substrate from one of the load lock chambers, transfers it to the process chambers in a prescribed sequence, and then returns it to a load lock chamber. The load lock chambers are designed to hold only a single substrate.
A plurality of said load lock chambers and/or said process chambers are provided and are stacked up in at least one place around the periphery of said separation chamber. Each of the load lock chambers incorporates a substrate holder that holds just a single substrate.
According to another aspect of the present invention, the substrate processing apparatus is configured so that said substrate holder has a shape that facilitates the alignment of substrates whereby they are always held at the same position.